The present invention relates to systems and methods for evaluation of the self-diagnostic functions of an electronic controller for a motor vehicle and its engine.
The use of built-in microcomputers to control various functions of a motor vehicle and its engine is very prevalent. The advent of the microcomputer in this arena has opened greater possibilities for the diagnosis of problems with either the vehicle or the engine operation. In one specific example, the microcomputer carries out a short self-diagnostic program prior to starting the engine. In one application, this self-diagnostic program monitors the various condition sensors and electrical actuators during the operation of the engine and vehicle. During engine operation, the self-diagnostic program stores information concerning intermittent or temporary events or faults. Long-term or severe faults can lead to immediate error indications, such as a visible or audible alarm.
Although the intermittent or temporary faults may not be significant enough to warrant vehicle shut down there is still some value in being aware of the occurrence of these events. In order to address this need, many self-diagnostic programs have means for initiating an annunciator flash-out of active faults. For example, if the annunciator is a panel of fault lamps, portions of the self-diagnostic routine will allow the service personnel to sequence through the fault lamps. As each lamp is sequentially illuminated, the stored error conditions can be manifested by a flashing warning signal. In another approach, the array of fault lamps can be illuminated to depict various diagnostic fault codes. Different approaches to displaying the fault codes can be taken. For instance, the self-diagnostic program can automatically iterate through the code sequences for all of the known faults. In another approach, the diagnostic technician must manually increment through the fault code sequences.
In a typical vehicle installation, the self-diagnosis feature of the vehicle microcomputer is initiated by a pair of hardware switches mounted inside the vehicle cab. One switch can be energized to cause the microcomputer to enter the self-diagnostic mode. The second switch can be used to increment through the fault code sequence.
One detriment associated with this approach is that additional hardware is required, namely the pair of diagnostic switches. The additional hardware adds cost and increases the risk of reliability problems. There is a need for a system and method for controlling diagnostic annunciators that does not require additional hardware.